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Old 26th January 2003, 12:48 AM   #1
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Location: Australia
Default DIY Car Amp resources

I've been thinking now for a while about making a car amp but I've only found 2 pages that cover aspects of it.
Does anyone know any more to add the to list?
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Old 26th January 2003, 05:00 PM   #2
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Default a lot of DIY car amps

are built off the LM3875 or LM3886 chips -- in my old MB I had one with a switching power supply to provide +/- 36 volts. do a search on either of the above as there are quite a few single chip designs.

if you go to Steve Bench's website (just do a google search) you will find a mobile tube amp - or at least the power supply thereof.

I think that there are a lot of tire-kickers for the switching amps from National Semi and Texas Instruments. I haven't had time to play around with these chips.

Unless you own a Bentley, Rolls or MB500 you can live with a lot more noise and THD in a car amp. Don't get overly anxious about THD stats if you're driving around in a VW Cabrio.
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Old 27th January 2003, 07:37 AM   #3
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the LM3875 or LM3886 chips is BAD !! for car amplifier...

u can build a Good amp... for 4 Speakers in the car us in :
TDA7560 50Wx4 Max~4 Ohm / 80Wx4 Max~2 Ohm MOSFET

and for the sub in the car us in:
TDA1562Q 70Wx1 Max

it is simple to build !.
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Old 27th January 2003, 08:36 AM   #4
Vigier is offline Vigier  Netherlands
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Hi BassAmp,

can you tell me what's wrong with the LM3886 in a car?
The TDA7560 and the TDA1562Q are able to work at 12V, and the LM3886 needs an SMPS... is that the only problem? The specs of the LM3886 are MUCH better than the specs of the TDA's!

If frost doesn't care about building an SMPS, then he's got a MUCH better amp!

Grtz, Joris
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Old 27th January 2003, 10:17 AM   #5
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OK... Soo.. The specs of the STKxxxx are MUCH better than the specs of the LM3886! and it easy to build !

LM3886 is dont good for car subs...... !
STK is a stronger than LM3886...

STK4231 II 100w RMS + 100w RMS
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Old 27th January 2003, 12:30 PM   #6
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if you have to, the LM3886 can be bridged for more power and the chip is 1/3 the price of the Phillips Class H chip. (the bridging circuit is on National Semi's website.)

The Phillips chip is only available from Future-Active in the U.S. so you'll have to order 50 if you're in the states. the situtation in Europe or Aussie/NZ and elsewhere is probably different.
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Old 27th January 2003, 07:50 PM   #7
e96mlo is offline e96mlo  Sweden
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I have noticed that it is common practice for Dj BASS AMP to use only output power to determine how good an amplifier is.

I once saw a car amp that could produce 20 kW for a microsecond or so into a short. Probably the best amp ever.

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Old 27th January 2003, 08:51 PM   #8
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Default from today's Wall Street Journal

<b><em>New 'Extreme' Sport:
Blasting Car Radios</b></em>

If you could somehow make your car stereo system as loud as a locomotive engine, you would still have a long way to go before you would impress Wayne Harris.

Mr. Harris is the owner and impresario behind dB Drag Racing, a rapidly growing group of enthusiasts who take the love of gadgets to startling heights. The group lives in an alternative technology universe far removed from the polite world of middle-class laptops and PDAs.

"DB" stands for decibels. In dB Drag Racing, the winning car is not the fastest, but the one with the loudest stereo system. Mr. Harris lords over this world, incongruously, from here in Coeur d'Alene, Idaho, an upscale lakeside development for people who want to escape city life and all its noise.

Actually, dB draggers say they frown on driving around disturbing the peace. Indeed, dB Drag racing contests have little resemblance to the bass-thumping duels on urban street corners on a Saturday night. In dB Drag Racing's top category of competition-called, logically, "Extreme"-vehicles are completely rebuilt to turn them into decibel factories.

They may contain dozens of subwoofers, each with their own amplifier, requiring enough total power to run four or five houses. Power cables are as thick as garden hoses. One contestant built his own subwoofer -- six feet in diameter. It blew out the lights on top of his truck.

That's just the start. The car's doors are often filled with concrete -- and concrete is sometimes even poured on the floor -- to help keep the precious sound pressure inside, where the volume is measured. Normal car windows are replaced by glass several inches thick, for the same reason.

All that reinforcing means that if you are standing outside a car with its windows rolled up, as they are in competition, it will sound rather quiet, relatively speaking.

By the time a car -- or more typically, a van -- is ready for Extreme dB Drag Racing competition, it can weigh six tons. Most aren't actually driven on the street. The owners, usually a team of dB Drag buffs, truck the car around to competitions.

At decibel-measuring time, the team of owners will stand around their car, leaning in hard against its doors and windows. Some of them will even lie spread-eagled on the roof. All this keeps the frame from vibrating, and adds several fractions of a decibel to the score.

"It is quite a spectacle," says Mr. Harris.

DB Drag racing has its finals once a year in Nashville, Tenn. This isn't just another case of Americans' car fetish; a quarter of the group's 20,000 members are from overseas.

In fact, last year's competition was won in an upset by a team from Germany, who rang up 177.7 decibels, beating the favored team from Ozark, Mo., by 1.8 decibels. Because raising sound by just three decibels requires a doubling of power, the victory margin was something of a Nixonian landslide.

How did the Germans do it? No one really knows. They put up curtains inside their van's windows to hide their trade secrets. The judges, though, were at least able to check that they didn't cheat, like the contestant who once exploded his air bag in a competition, illegally gaining several extra decibels.

A decibel level of 177.7 ostensibly is as loud as a 747 at 50 feet, though Mr. Harris says such comparisons are misleading, because a jet puts out its sonic energy all across the spectrum, not just in one small part if it, as happens with the bass frequencies used exclusively in dB Drag.

Still, it is very, very loud. If you opened up the van's doors and turned up the volume, it would sound like artillery fire.

Mr. Harris, who is 41 years old, has been involved in loud cars since he was an engineering student in Texas. He worked for two decades at Rockford Fosgate, the big Tempe, Ariz., car-audio company, designing products, writing articles and making speeches, eventually becoming a superstar in the world of the cars that go boom.

He now does dB Drag Racing full time. There will be hundreds of dB Drag competitions this year, leading up to the finals; most are sponsored by car-stereo dealers.

Mr. Harris has long had licensing deals from all the big car-audio manufacturers. But he worries that after six years, the sport has reached its limit as a grass-roots phenomenon.

He wants some sponsor, he says, "to take it to the next level." Some corporate type like Mountain Dew, perhaps, or even Microsoft selling X-box videogames. There would be a big dB Drag Racing semi, and it would go on a national tour. "We have the demographics," he says.

It's probably inevitable. All things extreme have become a staple, even a cliché, for advertisers. The phenomenon of "The Fast and Furious," the street-racing movie, didn't hurt, either.

But would such a tour visit Mr. Harris's town? The streets here in Coeur d'Alene are so quiet, you can hear anything, even the soft clicking of someone dialing police to complain about the loud car stereo that just drove by.
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Old 28th January 2003, 02:29 AM   #9
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The latest attemps/projects in australia to break that record involve about 10 1.5kw amps all stable at 0.5ohms not to mention a fair few subs.
Although DB drags are fun that wasn't what I was going for.
I started a previous thread about getting a P3a stable at 2 ohms which now I think its gonna be 1 ohms in the end.
I don't mind making a SMPS although pulling 150 amps from a car battery is a little daunting :/
If I can get a p3a stable @ 1 ohms & 1 kw rms it only leave the midrange/tweeters to provide for. Is there a lowish power design (50-100w) with extremly low distorion (0.00x%)? Class A is out due to inefficienties so Class AB is probly my best bet.
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Old 28th January 2003, 02:36 AM   #10
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Default if it were an MB

I recall from my old MB that the door seals were so good (save for the winter) that your ears would feel the pressure change when they were closed quickly, so you aren't dissipating pressure.

I would venture to guess that it has a lot to do with plugging leaks as in any pressurized system -- isn't this why we tune a port, or an exhaust?
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